error in window.cpp (QT) (Bug #495)

Very strange code in window.cpp file in highgui module:

_//-------- Qt ---------
CV_IMPL void cvAddText( const CvArr*, const char*, CvPoint org, CvFont font) {
CV_NO_GUI_ERROR("cvAddText");
return -1;
}

CV_IMPL void cvDisplayStatusBar(const char* name, const char* arg2, int arg3) {
CV_NO_GUI_ERROR("cvDisplayStatusBar");
return -1;
}

CV_IMPL void cvDisplayStatusBar(const char* name, const char* arg2, int arg3) {
CV_NO_GUI_ERROR("cvDisplayStatusBar");
return -1;
}

CV_IMPL void cvCreateOpenGLCallback(const char* name, cvOpenGLCallback callback, void* param) {
CV_NO_GUI_ERROR("createOpenGLCallback");
return -1;
}
...._

Functions with 'void' specificator can't return a value.